Summary

• normalize Pi ACP initialize requests by coercing string protocolVersion values to JSON numbers before forwarding
• normalize Pi ACP session/new requests by ensuring params.mcpServers defaults to [] when omitted
• add a regression test using a strict Pi stub that fails without these normalizations
• document custom Pi binary configuration in CLI docs (PI_ACP_PI_COMMAND, PATH, and symlink strategies)
• update quickstart docs to list all supported agent IDs and include pi/cursor in preinstall examples

Why

Pi ACP bootstrap could fail end-to-end when callers sent protocolVersion as a string and/or omitted mcpServers in session/new.

Separately, users running forked/custom Pi binaries need documented override options for how pi-acp resolves the pi command, and quickstart should clearly list the supported agents.

Testing

• cargo test -p sandbox-agent --test v1_api acp_transport::pi_initialize_and_session_new_are_normalized -- --nocapture
• cargo test -p sandbox-agent --test v1_api -- --nocapture